During a surgical procedure, it is important to maintain the operative site clean, antiseptic, and free of debris. One common technique for maintaining such a surgical site is to irrigate the site with an irrigation or antiseptic solution. Typically, the irrigation liquid (e.g., saline) is supplied from a reservoir through a tubing to a dispensing handle that is manipulated by a physician, assistant, or attendant. Spent irrigation liquid and other debris that may collect at the irrigation site may be removed by applying a suction to the irrigation site.
A number of combination irrigation and suction devices have been used and proposed. Many deliver irrigation liquid in a pulsatile manner to dislodge debris, and aspirate the site to remove the irrigation liquid and other liquids that collect at the surgical site. One such pump is shown, for example, in co-pending U.S. patent application "Pulsed Lavage Pump with Integral Power Source and Variable Flow Control" to Pasche et al. (Ser. No. 08/389,155, filed Feb. 15, 1995). The Pasche device generally includes a tubing having a first end that is connectible directly to a reservoir, and a handpiece that is connectable directly to the second end of the tubing. All of the components for energizing an internal pump, pumping the irrigation liquid, and controlling the operation of the pump are contained within the handpiece.
Among many other elements, the Pasche handpiece generally includes a housing that contains a variable volume chamber liquid pump, a constant speed D.C. motor to actuate the pump, batteries to energize the motor, and a trigger pivotally mounted to the housing. The trigger acts as a switch between the batteries and motor, and also controls the volume and pressure of irrigation liquid emitted by liquid pump. The pump includes a reciprocating bellows for providing a pulsatile irrigation stream that first draws irrigation liquid from an external reservoir into a valve housing during a filling stroke, and then ejects the liquid from the valve housing during a pumping stroke. The volume and pressure of liquid that is emitted during each pulsing cycle is dependent on the length of stroke effected by the bellows. The trigger controls the stroke of the bellows, and thus the volume and pressure of emitted liquid, by means of a control linkage. As the trigger is depressed inwardly, the control linkage continuously increases the pumping stroke of the bellows, thus increasing the volume and pressure of irrigation liquid emitted by the pump. In order for irrigation liquid to be emitted at a constant volume and pressure, however, the trigger must be maintained in a fixed position. To that end, the pumping system includes an arrangement for locking the trigger in a single fixed position that delivers irrigation liquid at a maximum volume and pressure. This locking arrangement nevertheless does not permit the trigger to be locked in a fixed position that delivers irrigation liquid at constant, non-maximum volumes and pressures. It would thus be desirable to provide an entirely self-contained pulsatile suction and irrigation device that facilitates the delivery of irrigation liquid at one or more preset, non-maximum volumes and pressures.
As noted above, the trigger acts as a switch between the batteries and the motor. To that end, the trigger includes a camming surface near the trigger pivot. When the trigger is depressed inwardly a preselected distance, the camming surface urges a first conductive contact into contact with a second conductive contact to electrically connect the motor to the batteries. This energizes the motor which actuates the pump. Since the stroke of the bellows, and thus the volume and pressure of liquid emitted by the pump, is controlled by the mechanical position of the trigger (i.e. the preselected distance), it is desirable for the preselected distance to be preset during manufacture to a relatively small distance so that first stroke of the bellows is relatively small. This causes the pump to emit liquid at a relatively low pressure and volume, consequently providing the pump with a wider range of pumping volumes and pressures than if the preselected distance is relatively large. During manufacture, however, this preselected distance is difficult to accurately preset because the camming surface is very close to the trigger pivot. According to known leverage principles, even if the trigger is depressed a relatively large distance, the distance that the camming surface may travel still can be very small. A seemingly trivial variation in such a small distance can therefore significantly affect the operation of both the pump and control mechanism. Consequently, two seemingly identical suction and irrigation handpieces having such a contact arrangement undesirably could have different preselected distances. One handpiece therefore could energize with only a slight depression of the trigger (emitting liquid at very low pressures and volumes), while the other handpiece could energize with only a relatively large depression of the trigger (not emitting liquid at very low pressures and volumes). In addition, the first and second contacts can permanently bend due to the forces applied by the camming surface, thus causing the motor to energize at varying, unanticipated positions of the trigger. This undesirably can cause the handpiece to lose a range of operational volumes and pressures for emitted irrigation liquid. It therefore would also be desirable to have a suction and irrigation handpiece that may be more easily manufactured to uniformly energize the pump at a preset position of the trigger.